Coordination of full actuated traffic controllers



March 10, 1970 ID JR" ETAL 3,500,308

COORDINATION OF FULL ACTUATED TRAFFIC CONTROLLERS Filed May 23, 1966 4Sheets-Sheet 1 B FIG.| I IDIII a 03 I01 K LC-I I 5 zIpFuLL I I I I 2FULL ACTUATED A AC UATED LoCAL MC LoCAL CoNTRoLLER ,2 CoNTRoLLERCOORDINATION MAsTER COORDINATION UNIT CONTROLLER UNIT (DA PREVENT P IINTERVAL No.2 A VARIABLE MAxIMuM TIME OUT INTERvAL No. a Fl 4 sET UP IANTERVAL I G /No.I P I f 3 B CLEARANCE I: /|NTERVAL No. a H IT C-L E AFII\T6 TIME SET UP (pa cps VARIABLE IN ERMAI. PREVENT I MAxIMuM TIME No.5 /INTERvAL I ouT INTERVAL No.7 34 No. 6 I

I INVENTORSI I RALPH M. RIDDLE, JR. a P I LOREN E PUCK CD3) I i I My,7M8 8nd Rs I I .ATToRNEYs March 10, I970 RIDDLE, JR" ETAL 3,500,308

COORDINATION OF FULL ACTUATED TRAFFIC CONTROLLERS Filed May 23. 1966 4Sheets-Sheet 2 MC T F|G.2

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JR. ET AL 3,500,308

4 Sheets-Sheet 3 (1)5 OUTPUT FIG. 2A

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RALPH M. RIDDLE, JR. 8 l 9REN F. PUCK Maya, 7116 8 Body ATTORNEYS UnitedStates Patent Int. Cl. G08g 1/08 US. Cl. 340-35 19 Claims ABSTRACT OFTHE DISCLOSURE There is disclosed a coordination unit for coordinatingthe operation of a full actuated trailic controller in an interconnectedsignalized system wherein the controller serves to control a trafficsignal which displays go, caution and stop intervals to at least twotraffic phases each having associated therewith tratfic detector meansfor detecting traffic in that phase and registering traific demand withthe controller. Also, the controller includes go interval terminationmeans associated with each phase for terminating, when energized a gointerval display to the associated phase. The coordination unit includesa coordi nation dial for cyclically timing a background cycle having apredetermined time duration; key means for dividing the background cycleinto at least two successively timed intervals associated with each ofthe traffic phases; and, circuit means each being associated with one ofthe traffic phases and being responsive to one of the timed intervals tothereby terminate a go signal displayed to that associated phase.

This invention relates to the art of tratfic control and, moreparticularly, to apparatus and method for coordinating the operation offull actuated local traflic controllers with other local controllers inan interconnected, progressive, signalized system.

A full actuated local traffic controller has associated therewithtrafiic actuatable detectors for each trafi'ic phase, i.e., movement,being controlled. Thus, a threephase, full actuated traffic controller,for controlling traffic flow through an intersection of three trafficphases, has associated therewith at least one detector for each phasefor detecting traflic, i.e., vehicles, in that phase, and registeringtraffic demand with the controller. The controller serves to allocateright-of-way intervals by means of a signal light located at theintersection to each of the phases in accordance with traffic demand. Asemiactuated traiiic controller is similar to a full actuated trafficcontroller, but at least one phase is a nonactuatable phase; that is,there is no detector associated with that phase. The nonactuatablephase, usually reserved for phases having heavy traliic flow, such asmain street, is allocated a minimum fixed time right-of-way interval bythe controller during each cycle of operation, with right-ofwayintervals being allocated to the actuatable phases dependent on trafficdemand. Thus, a full actuated tratfic controller allocates right-of-wayintervals in a more ethcient manner than a semiactuated controller,since the latter must allocate a minimum right of-Way interval to thenonactuatable phase during each cycle of operation whether there istratfic demand on that phase or not.

Frequently, municipalities require that all of the local controllers atvarious street intersections, whether the controllers be full actuated,semiactuated or pretimed controllers, be interconnected in a coordinatedsignal system supervised by a master controller. The purpose ofcoordinated operation of local intersection controllers is to obtain asmooth progression of traflic within the signal sys- "ice term. In sucha coordinated signal system, the maximum time length of the trafficsignal cycle of each of the interconnected local controllers isdetermined by the time length of a background cycle established by amaster controller. The background cycle may in turn be determined by apretimed or programmed schedule, or on the basis of varying trafiicdemands, as registered with the master controller by vehicle detectorslocated at various locations in the signal system.

Heretofore, coordination of actuated local controllers has been directedto coordination of semiactuated local controllers, or full actuatedlocal controllers, which for purposes of coordination have beenconverted to semiactuated local controllers, with the end result beingto allocate a fixed minimum amount of right-of-way time to main streettraflic flow to facilitate traffic flow through the intersections alongthe main street. Both semiactuated and full actuated trafiic controllersnormally include maximum time-out circuits for the actuatable phase, orphases, which serve upon the completion of predetermined time toterminate allocation of a right-of-way interval to the actuatable phase,whereupon a timed caution interval is allotted to that phase, afterwhich that phase is denied right-of-way movement during that cycle.

Coordination of such actuated controllers is accomplished with acoordination unit associated with each controller. Such a coordinationunit determines the proper time for releasing the controller to endallocation of a right-of-way interval to the nonactuatable phase afteran actuation has occurred on an actuatable phase, and for forcing thecontroller to terminate allocation of a rightof-way interval to anactuatable phase and commence allocation of a right-of-way interval tothe nonactuatable phase. In order to maintain efficient traffic flowwithin the signalized system, the point in time, during the masterdetermined background cycle, that the right-of-way interval of anonactuatable phase is terminated, must be accomplished at the propersplit of the cycle as determined by the master controller. The mastercontroller, which may be traific adjusted, serves to determine the mostefiicient trafiic cycle duration, the best division of the cycle betweenmain street and cross street traffic, and the most effective offset ofthe start of the cycle at each succeeding intersection. After theseparameters are determined they are imposed on each interconnected localcontroller in the coordinated signal system by means of the coordinationunits.

Coordination units known heretofore for coordinating the operation ofactuated local controllers generally include a motor driven wheel, knownas a coordination dial, carrying a plurality of switch actuatingelements, known as keys. The time cycle length to complete onerevolution of the coordination dial corresponds with the time length ofthe background cycle determined by the supervising master controller.One revolution of the coordination dial times one complete trafficsignal cycle for the associated traflic controller. One of the keys,known as the release key, is placed at or near the zero point or releasepoint of the coordination dial, and serves to initiate termination ofallocation of a right-of-way interval to the nonactuatable phase afteran actuation has occurred on an actuatable phase. A second key, spaced apredetermined angular distance from the release key, and known as asplit key or maximum time out key, serves to initiate termination ofallocation of a right-of-way interval to an actuatable phase if aright-of-way interval has not been previously terminated by lack ofdetector actuations. The release key serves once during each revolutionof the coordination dial to actuate a switch which connects a source ofpower to a timing circuit in the controller associated with thenonactuatable phase, such as to the plate circuit of a vacuum tube in anRC timing circuit or to a step switch driver coil. This causes thetiming circuit for the nonactuatable phase to terminate its timingfunction and thereby terminate allocation of a rightof-way interval tothe nonactuatable phase, whereupon the controller then normally times acaution clearance interval for the nonactuatable phase, after whichrightof-way movement is denied to the nonactuatable phase during thatcycle. Similarly, the maximum time out key, or split key, serves onceduring each revolution of the coordination dial to actuate a secondswitch which serves to connect a source of power to a second timingcircuit in the controller associated with the actuatable phase. Thiscauses the timing circuit to terminate its timing function, whereuponallocation of a right-of-way interval to the actuatable phase isterminated, which is normally followed by a timed clearance interval,after which rightof-way is denied to the actuatable phase.

The purpose of such a coordination unit as described above is toallocate during the background cycle a fixed minimum amount ofright-of-way time to the main street, or nonactuatable phase, tofacilitate traffic flow along the main street through the variousintersections. Accordingly, the time lapse during the background cyclefrom the point in time at which the maximum time out or split keyactuates the switch associated with the actuatable phase, to the pointin time at which the release key actuates the switch associated with thenonactuatable phase, is the guaranteed period of time during thebackground cycle that a right-of-way interval is allocated to mainstreet traffic flow. The time lapse from the point in time at which therelease key actuates the switch associated with the nonactuatable phase,and the point in time at which the maximum time out or split keyactuates the switch associated with the actuatable phase, is thepotential period of time during the background cycle that a rightof-wayinterval may be allocated to cross street traffic flow. The vehicledetector associated with the actuatable phase must be actuated prior tothe release point in the background cycle before a right-of-way intervalcan be actually allocated to the actuatable phase. If the vehicledetection on the actuatable phase occurs at a point in time just afterthe release point in the background cycle, the actuatable phase will bedenied right-of-way movement until the next cycle of operation, orsubstantially the entire time period of the background cycle which, forexample, may be on the order of 120 seconds. A further disadvantage ofprevious methods of coordinating the operation of semiactuatedcontrollers or full actuated controllers, which have been converted tosemiactuated controllers for coordination purposes, is that when crossstreet traffic flow is heavy and main street traffic flow is light,trafic on the cross street must be denied right-ofway movement while theguaranteed right-of-way interval is allocated to the main streetalthough there may be little or no traffic demand on the main street.

The present invention is directed toward coordination of full actuatedtrafiic controllers in such a manner that the controllers are operatedfull actuated during coordination by a background cycle so that,contrary to previous methods of coordination, the controllers may yieldto the next phase any time there is a lull in traffic.

The" invention contemplates that the coordinated full actuated trafiiccontroller serves to control a traffic signal which displays go, cautionand stop intervals to at least two traffic actuatable phases, eachhaving associated therewith vehicle actuatable detector means forregistering traffic demand with the controller. The invention furthercontemplates that the controller includes go interval terminationcircuitry associated with each actuatable phase for terminating, whenenergized, a go interval to the associated actuatable phase.

In accordance with the broad aspects of the invention, the operation offull actuated trafiic controllers is coordinated by a background cyclehaving a time point for guaranteeing when each actuatable phasecontrolled by the full actuated controller is required to yield toanother actuatable phase in accordance with traffic demand.

Further in accordance with the invention, apparatus and method areprovided for dividing the background cycle into at least twosuccessively timed intervals, and for each phase: sensing whether thecontroller is allocating a go signal to the associated phase during thefirst interval, and if so, conditioning phase termination circuitrymeans to a condition whereupon when energized it will terminate the gosignal display; commence sensing for a trafiic actuation on anotheractuatable phase; and, energizing the phase termination circuit meansonly after termination of the second interval when such a trafiicactuation is sensed.

In accordance with a still further aspect of the present invention, thebackground cycle is divided so as to include, for each actuatable phase,a third potential interval of a maximum timed duration, during which thetraffic actuation sensing is continued until a traffic actuation issensed or the third interval is terminated, whichever occurs first.

The primary object of the present invention is to coordinate theoperation of a full actuated local controller so that the controlleroperates full actuated during coordination.

A still further object of the invention is to coordinate the operationof a full actuated local controller so that its cycle length ofoperation may vary with traffic demand, but not exceed the time durationof a background cycle.

A still further object of the present invention is to coordinate theoperation of a full actuated local controller so that during thebackground cycle it allocates go signal display time to the fullestextent in accordance. with traffic demand.

These and other objects and advantages of the invention will becomeapparent from the following description of the preferred embodiment ofthe invention as read in connection with the accompanying drawings inwhich:

FIGURE 1 is a plan view schematically illustrating a pair ofcoordinated, two phase, full actuated local traffic controllers and amaster controller within an intercon- GENERAL DESCRIPTION Referring nowto the drawings, wherein the showings are for the purpose ofillustrating a preferred embodiment of the invention only and not forpurposes of limiting same, FIGURE 1 schematically illustrates a pair oftwo phase, full actuated local controllers LC-1 and LC-2 interconnectedthrough coordination unit C-1 and C-2, respectively, with a mastercontroller MC in an interconnected, progressive, coordinated, signalizedsystem. Local controller LC-1 controls trafiic flow through anintersection of traffic movements, or phases A and B in accordance withtraific demand registered with the controller by vehicle actuatabledetectors D1 and D-3 for phase B,

phase A. Right-of-way, clearance and stop signals are displayed tophases A and C by means of a trafilc signal S2 connected to andcontrolled by local controller LC-2.

Referring now to FIGURE 2, there is schematically illustrated a mastercontroller MC connected to local controller LC-l for supervising theoperation thereof by means of coordination unit C-1. Coordination unitC-l, which will be described in greater detail hereinafter, takes theform of a three dial coordination unit, similar to that knownheretofore, for coordinating semiactuated trafiic controllers, andincludes three synchronous motor driven coordination dials CD-l, CD-2and CD-3, which are separately energized to rotate at different speedsand time different background cycles. Each coordination dial carries aplurality of keys P-l through P-7 and G extending radially outward fromthe dial. Preferably, the dial is provided with one-hundred equallyspaced, longitudinal slots extending around the circumferential surfaceof the dial so that the keys may be spaced from each other inpercentages of the background cycle. The keys carried by each dial serveto actuate suitable switches, generally designated as SW.

Coordination unit C-l may, in accordance with the present invention, beutilized in conjunction with various master controllers, and theinvention is not limited to any particular master controller. Normally,municipalities require that pretimed traffic controllers andsemiactuated controllers, when coordinated, be capable of operating atvarious cycle lengths in addition to a normal cycle length of operation.Accordingly, when such pretimed and semiactuated local controllers areto operate at a cycle length other than normal in a coordinated,progressive system supervised by a master controller, the mastercontroller should be capable of remotely selecting the cycle length ofoperation to be in effect for all of the supervised local controllers.

The master controller MC may be pretimed or traflic actuated, asdesired, the invention not being limited to either. For purposes ofsimplifying the explanation of the invention, the master controller MC,illustrated in FIG- URE 2, has been simplified and includes threesynchronization cam wheels 10, 12, and 14, respectively driven bysynchronous motors 16, 18 and 20, including suitable gearing, or thelike, so that when energized wheels 10, 12 and 14 rotate at differentspeeds. Motor 16 is normally connected across an energizing voltagesource V, and motors 18 and 20 are connected across source V by means ofnormally open coordination dial selector switches DS-2 and DS-3. Withswitches DS-2 and DS-3 in their normal open position, coordination dialCD-1 is in operation. Closure of dial selector switch DS2 serves toenergize circuitry within coordination unit C-1 for energizing onlycoordination dial CD-Z. Similarly, closure of dial selector switch DS-3serves to energize circuitry within the coordination unit C-l forenergizing only coordination dial CD3. A movable switch contact 22 rideson the peripheral surface of an associated synchronization cam wheel 10,12 or 14, and is normally in electrical engagement with a stationarycontact 24 for purposes of connecting voltage source V with ofi'setselector switches 0-1, O2 and O-3 connected to coordination unit C-l.Only one offset selector switch O-l, O-2 or O-3 is closed at any onetime, and serves to select the particular offset in effect in theprogressive, coordinated, signalized system. An arcuate slot 26 isprovided in the peripheral surface of each synchronization wheel 10, 12and 14. Once during each revolution of a synchronization wheel theassociated movable contact rides off the peripheral surface of the wheeland falls into the arcuate slot 26, breaking electrical contact with itsassociated stationary contact 24. This electrical break extends forapproximately 3% of a revolution and, as will be discussed in greaterdetail hereinafter, is used for synchronized purposes.

Coordination unit C-l may be used to coordinate the operation of anyfull actuated traflic controller having external maximum control. Thatis, the internal maximum timing function of the controller can bedisabled so that this function is timed by an external maximum timingdevice. Normally, semiactuated and full actuated traffic controllersinclude external maximum control for each actuatable phase beingcontrolled by the controller. The two phase, full actuated localcontroller LC-1 may, for example, take the form of two interconnectedphase units, each being constructed in accordance with that disclosedand illustrated in United States patent application, Ser. No. 463,449,filed May 21, 1965. For purposes of facilitating the understanding ofthe present invention, however, local controller LC-1, as illustrated inFIGURE 2, has been simplified to illustrate only that which is necessaryto understand the present invention. The local controller LC-l, asillustrated, includes a phase A memory circuit 30 connected to a voltagesource V, and has an input circuit connected to phase A vehicleactuatable detectors D-2 and D4, and an output circuit connected tocoordination unit C1. Similarly, the local controller LC-l also includesa phase B memory circuit 32 connected to voltage source V, and has aninput circuit connected to phase B detectors D-1 and D-3, and an outputcircuit connected to coordination unit C1. Each memory circuit serves,when its associated detectors have been actuated, to remember theactuation and complete a circuit to the coordination unit. Whereas thevehicle detectors have been illustrated as being spot detectors, such astreadle or magnetic detectors, the invention is not limited to same andthe detectors may take the form of presence detectors, such as loopdetectors or ultrasonic detectors. In the event that the detectors takethe form of presence detectors, memory circuits 30 and 3-2 may bebypassed since such presence detectors normally provide an output signalso long as a vehicle is present within the zone of detector influence.

Local controller LC-1 also includes means for connecting voltage sourceV with the coordination unit C-l so long as the phase A right-of-waysignal is being displayed by trafiic signal S-1 to phase A. For purposesof simplification, the means for accomplishing this function isillustrated as normally open switch 34 connecting source V with thecoordinated unit C-l. It is to be understood that switch 34 is closed byany suitable means so long as a right-of-way signal is displayed bytrafiic signal S1 to phase A. Similarly, normally open switch 36connects voltage source V with the coordination unit C-l, it beingunderstood that the switch is closed by any suitable means so long as aright-of-way signal is displayed by trafiic signal 8-1 to phase B.

Local controller LC-l also includes a phase A internal maximum timer 38,which normally serves to time the maximum duration that n'ght-of-way maybe allocated to phase A. The maximum timer 38 is connected acrossvoltage source V through a disabling switch 42 and relay coil CR1-C of arelay CR1. Relay CR1 also includes normally open relay contacts CR1-1,which serve upon energization of the relay to connect a phase A steppingswitch driver coil 40 across voltage source V. When the maximum timer 38completes its timing function a circuit is completed through disablingswitch 42 to energize relay CR1. This in turn energizes stepping switchdriver coil 40, which serves to actuate a suitable phase A step switch,designated generally at 44, which steps one step and in turn serves toactuate suitable phase A signal circuitry, designated generally at 46,for purposes of terminating allocation of a right-of-way interval tophase A and commence timing in phase A clearance interval, after whichphase A is denied right-of-way movement. During coordination, theinternal maximum timer circuit 38 is disabled by connecting thedisabling switch 42 to the phase A output circuit of coordination unitC-1 so that the maximum timing and, hence, termination of a phase Aright-of-Way interval, is externally controlled by the coordination unitC-1, to be described in greater detail hereinafter.

In a manner similar to that as discussed with respect to the circuitryassociated with phase A, the local controller LC-l also includes a phaseB internal maximum timer 48 normally connected across voltage source Vby means of a disabling switch '50, similar to switch 42 describedpreviously, and a relay coil CR2-C of a relay CR2. Relay CR2 alsoincludes normally open relay contacts CR2-1 which serve uponenergization of relay CR2 to connect a phase B step switch device coil52 across voltage source V. Step switch driver coil 52, in a mannersimilar to that discussed with respect to driver coil 40, serves uponenergization to actuate a suitable phase B step switch, designatedgenerally at 54, which in turn actuates suitable phase B signalcircuitry, designated generally at 56, for purposes of terminatingallocation of. a right-of-way interval to phase B and commence timing ofa phase B clearance interval, after which phase B is denied right-ofwaymovement.

Whereas the coordination unit C-l is preferably used in conjunction witha local controller LC-l having means, such as disabling switches 42 and50, for disabling the internal maximum timers associated with each phaseto permit the maximum timing function to be controlled by an externalmechanism, such as a coordination unit, the invention is not limited tosame. Thus, for example, it is contemplated that the coordination unitC-1 may be used in conjunction with a full actuated traflic controllerwherein the internal maximum timers are not disabled. With respect tolocal controller LC-l, illustrated in FIGURE 2, disabling switches 42and 50 may be replaced with jumpers so that the phase A output circuitof coordination unit C-l is connected to the junction of the outputcircuit of internal maximum timer 38 and relay coil CR1-C, and so thatthe phase B output circuit of coordination unit C-l is connected to thejunction of the output circuit of in ternal maximum timer 48 and relaycoil CR2-C. However, in the event that the local controller includessuch jumpers, the internal maximum timers must be set so that theywillnot complete their timing functions prior to the points in time duringthe background cycle at which the external timing is completed, i.e.,the points in time at which the phase A and phase B output circuits ofthe coordination unit C"-1 communicate energizing signals to energizerelays CR1 and CR2, respectively.

COORDINATION UNIT Having now briefly described a master controller and atwo phase, full actuated traific controller, reference is now made toFIGURE 3 wherein there is schematically illustrated a preferredembodiment of a coordination unit, constructed in accordance with thepresent invention, for purposes of coordinating the operation of a twophase, full actuated trafiic controller in such a manner that thecontroller may operate full actuated during coordination. Coordinationunit C-l generally comprises: coordination dial, offset synchronizingand control circuits H; background cycle divider circuit I; a phase Acoordination circuit I; and, a phase B coordination circuit K.

The coordination unit C-1, in its simpliest form, may include a singletimer for timing a particular background cycle for coordinationpurposes. The timer, for example, may take the form of a coordinationdial CD-l, driven by a synchronous motor M1, connected across voltagesource V for energization. It is contemplated, however, that thecoordination unit C-l, for greater flexibility, in coordinating theoperation of a full actuated traflic controller, has the capability oftiming different background cycles. This capability is common tocoordination units known heretofore for purposes of coordinating theoperation of pretimed and semiactuated traflic controllers. Toaccomplish this and other capabilities, the coordination unit C-1 alsoincludes: additional coordination dials CD-2 and CD-3 driven bysynchronous motors M2 and M3, respectively; dial motor select controlcircuitry 56; dial motor select switching circuitry 58; offset and syn-8 chronization control circuitry 60; and, synchronization switchingcircuitry 62. As is conventional in previous coordination units for usewith pretimed and semiactuated controllers, coordination dial CD-l isnormally in operation during coordination for cyclically timing a firstbackground cycle.

As illustrated in FIGURE 3, the dial motor select switching circuitry 58and the synchronization switching circuitry 62 are interconnected andserveyto connect motors M1, M2 and M3 across voltage source V. The dialmotor select circuitry. 58 includes circuit means, such as relays andthe like, which are ineffective to change the operation from motor M1 tomotor M2 or ,motor M3, except during the period that an associated camcircuit No. 1 is closed. Cam circuit No. 1 connects the dial motorselect control circuitry 56'across voltage source V to permitenergization of circuitry 56 when-the cam circuit is closed, as will bedescribed in greatendetail hereinafter. If coordination dial selectorswitch DS-2. or switch DS-3, in the master controller MC, is closed,circuitry 56 will be effective when cam circuit No. 1 is closed toenergize suitable circuitry, such as relay contacts, in the dial motorselect switching circuitry 58 for disconnecting the voltage sourceV frommotor M1 and connecting the source to motor M2 if-switch DS-Zis closed,or motor M3 if switch DS-3 is closed. In addition, coordination unit C-1includes offset and synchronization control circuitry 60 connected withoffset selector switches O-1, O-2 and O-3 in the master controller MC.Switches O-l, 0-2 and O-3 serve when closed to actuate suitablecircuitry, such as relays, in the offset and synchronization controlcircuitry 60 to establish different offsets; such as average, inboundpreferential, or outbound preferential. Suitable circuitry, such asrelay contacts, in the synchronization and switching circuitry 62 isresponsive to the operation of the offset and synchronous controlcircuitry 60 for establishing the oifset relationship selected byclosure of one of offset selector switch O-l, 0-2 or O-3.

In addition to the foregoing, the coordination unit also includes thecapability, known to prior coordination units, for maintaining eachlocal controller in synchronism with the master controller. This isaccomplished with the synchronizing cam wheels 10, 12 and 14 in themaster controller, which, as previously discussed, each include anarcuate cutout portion 26 which breaks an energizing circuit to theoffset selector switches O-1, O-2 and O-3 for 3% of the background cyclein effect. The synchronizing wheels 10, 12 and 14 are driven at speedscorresponding with the background cycle in effect, i.e., motor 16 isenergized when coordination dial CD-l is in effect and drivessynchronizing wheel 10 at the same speed as dial CD-1 is driven by motorM1. Similarly, synchronizing wheels 12 and 14 are respectively driven atspeeds corresponding with the background cycles timed bycoordinationdials CD2 and CD-3. Power from the master controller is normallysupplied through the offset selector switches O-l, 0-2 and O-3 forapproximately 97% of the background cycle. A key, not shown, carriedbythe coordination dial opens a switch in circuitry 60' for approximately1% of the background cycle. If this interruption occurs during theperiod that power from the master controller is normally interrupted,i.e., for 3% of the cycle, it will not interrupt the operation of motorsM1, M2 or M3, since such an occurrence is indicative that the localcontroller is operating in synchronism with the master controller.However, in the event that the interruption occurs during the 97%eriodof the background cycle that power is supplied from the mastercontroller through the offset selector switches O-1, O-2 and O-3, thenthe synchronization control circuitry 60 is effective to de-energize themotor M1, M2 or M3 in operation to stop rotation of the associatedcoordination dial. As soon as the 3% interruption in power from themaster controller occurs, the synchronization control circuitry servesto re-energize the selector motor M1, M2 or M3 so that the coordinationdial in effect may commence rotation for timing the background cycle insynchronization with the supervising master controller.

Since the features of coordination dial select, offset andsynchronization of control circuit H are common with previouscoordination units, the complete circuitry for obtaining the notedfunctions has been omitted for purposes of simplifying the understandingof the present invention. For more detailed information as to thecircuitry involved, reference may be made, for example, to acoordination unit illustrated and described in United States Patent No.3,196,387, as well as to the offset, split and synchronization featuresof a system illustrated and described in United States Patent No.3,133,264, all assigned to the assignee of the present invention.

Referring now to FIGURE 4, there is schematically illustrated the frontface of coordination dial CD-1. The coordination dial preferablyincludes a cylindrical drum having longitudinal slots extending parallelto the axis of symmetry and spaced arcuately around the circumferentialsurface of the drum to define one-hundred equally spaced slots. Thus,keys may be placed in the slots spaced from each other in percentages ofthe background cycle. As shown in FIGURE 4, keys P1, P2, P-3, P-4, P5,P6, P-7 and G extend radially outward from the circumferential surfaceof coordination dial CD-l.

BACKGROUND CYCLE DIVIDER CIRCUIT 'able contacts 64 and 68 are connectedtogether in series with a step switch driver coil 72 of a suitable stepswitch 74. Stationary contact 70 is connected to one side of voltagesource V so that when contact 68 engages contact 70 a circuit iscompleted across voltage source V for energizing driver coil 72. Thestep switch 74 includes, in addition to driver coil 72, a ratchetmechanism, not shown, and a contact carrying camshaft, not shown, whichserve to complete normally open cam circuit Nos. 1, 2, 3, 4, 5 and 6 inresponse to energization of the driver coil 72, in accordance with thecam circuit-interval chart illustrated in FIGURE 5. As will be notedfrom the chart, the step switch steps, during each repetition of thebackground cycle, through eight intervals, numbered 1 through 8 on thecam chart. Thus, for example, in

response to actuation of movable contact 70 by key G to engagestationary contact 70, the step switch driver coil is' energized,resulting in the step switch advancing to interval No. 1 during whichcam circuits Nos. 2 and 3 are completed. Cam circuit No. 2 serves toconnect stationary contact 66 with one side of voltage source V and ismaintained completed throughout interval Nos. 1 through 7 by a cam, notshown, located on the camshaft of step switch 74. With cam circuit No. 2completed, each time that movable contact 64 is actuated by keys P-1through P-7 a circuit is completed to energize the step switch drivercoil 72. With reference to the cam chart, it will be noted that camcircuit No. 4 is completed in response to key P-2 actuating contact 64,that cam circuit No. 5 is completed in response to key P-4 actuatingcontact 64, and cam circuit No. 6 is completed in response to key P-6actuating contact 64. During the time between interval Nos. 8 and 1, keyG actuates contact 68, and cam circuit No. 1 is completed for purposesof permitting dial motor select control circuitry 56 to affect a dialchange from coordination dial CD-l to coordination dial CD-2 or CD-3, inaccordance with closure of dial select switch DS-2 or DS-3 in the mastercontroller MC.

1 0 COORDINATION CIRCUITS Reference is now made to the phase Acoordination circuit J illustrated in FIGURE 3. Circuit J includes anormally de'energized relay CR3 having a relay coil CR3-C connectedacross voltage source V by means of a resistor 76. Resistor 76 places abias, or floor potential, on relay coil CR3-C which is not sufficient toeither pull in or hold in the relay, and serves the purpose to preventresidual magnetism from accumulating in the relay during operation.Relay coil CR3C is also connected through normally open cam circuit No.3 to normally open switch 34 in local controller LC1. Switch 34represents, when closed, that a right-of-way signal is being displayedto phase A by local controller LC-l, and during such period completes acircuit to the cam circuit No. 3 for energizing coil CR3-C duringinterval No. 1, see FIGURE 5, when cam circuit No. 3 is completed. RelayCR3 also includes normally open relay contacts CR3-1 and CR32.Relaycontacts CR3-1 serve, when closed upon energization of the relay,to shunt cam circuit No. 3 to provide a holding circuit for maintainingcoil CR3-C energized so long as switch 34 in local controller LC-l isclosed. The movable element of normally open relay contacts CR3-2 isconnected in series with cam circuit No. 4 to the junction of themovable element of relay contacts CR3-1 and the normally open switch 34in local controller LC1. The stationary element of relay contacts CR3-2is connected through normally open relay contacts CR4-1 to the phase Aoutput circuit of coordination unit C1, which leads to the phase Adisabling switch 42 in local controller LC-l. Relay contacts CR4-1 areclosed in response to energization of relay coil CR4-C of relay CR4,which has its energizing circuit completed when phase B memory circuit32 in local controller LC-l is energized in response to actuation ofeither of its associated phase B vehicle actuatable detectors D-l orD-3.

The phase B coordination circuit K, illustrated in FIG- URE 3, issubstantially identical to the phase A coordination circuit I, describedabove. Circuit K includes a normally de-encrgized relay CR5 having arelay coil CR5C and a pair of normally open relay contacts CR51 andCR5-2. Coil CR5-C is connected across voltage source V by means of aresistor 78 which, in a manner similar to resistor 76 discussedpreviously with respect to circuit 1, places a bias, or floor potential,on relay coil CR5-C which is not sufiicient to pull in or hold in therelay, and serves to prevent residual magnetism from accumulating duringoperation. The junction of resistor 78 and coil CR5-C is connected tonormally open phase B right-ofway signal switch 36 in local controllerLC-l by means of cam circuit No. 5. Relay contacts CR5-1 serve, whenclosed, to shunt cam circuit No. 5 to provide a holding circuit forrelay coil CR5-C to maintain the relay energized so long as aright-of-way signal is being displayed to phase B, as represented byclosure of switch 36. The movable element of relay contacts CR5-2 isconnected to the junction of the movable element of relay contacts CR5-1and normally open switch 36 by means of cam circuit No. 6. Thestationary element of relay contacts CR5-2 is connected through normallyopen relay contacts CR6-1 of relay CR6 to the phase B output circuit ofcoordination unit C-l which leads to the phase B disabling switch 50 inlocal controller LC1. Relay contacts CR6-1 are closed upon energizationof relay coil CR6-C, which has its circuit completed for energizationwhen the phase A memory circuit 30 is energized in response to actuationof either of its associated phase A vehicle actuatable detectors D-2 orD-4.

OPERATION For coordination operation of local controller LC-l, internalmaximum timer disabling switches 42 and 50 are respectively transferredfrom the positions as shown in FIGURE 2 to be in circuit with the phaseA and phase B output circuits of coordination unit C-1. Depending on thebackground cycle in eflfect, one of the coordination dials CD-1, CD-2 orCD-3 of coordination unit C-1 is in operation. If the coordination dialselector switches DS2 and DS3 in the supervising master controller MCare in the open position, as illustrated in FIGURE 2, coordination dialCD-1 is in operation to time a particular background cycle. Duringcoordination operation the cycle length of operation of local controllerLC-1 may vary with traflic demand, but will never exceed the time lengthof the background cycle timed by coordination dial CD-l. Withcoordination dial CD1 in operation, motor M-16 in master controller MCis in operation for synchronizing purposes. One of the offset selectorswitches -1, 0-2 or O3, associated with motor M-16 in the mastercontroller MC, is closed representative of the particular otfset ineffect.

Coordination dial CD-l rotates to cyclically time the background cycle,the time duration to complete one revolution of the dial; the elapsedtime and direction of dial rotation being indicated by the arrows inFIGURE 4. During each revolution of dial CD-1, key G actuates movablecontact 68, see FIGURE 3, to engage stationary contact 70, completing acircuit for energizing step switch driver coil 72. This advances stepswitch 74 to interval No. 1, see FIGURE 5, during which cam circuit Nos.2 and 3 are completed. The time lapse of this interval is determined bythe spacing from key G to key P-1, and may be termed as the phase Asetup interval. During this timed interval, relay coil CR3-C in circuitI will become energized if a right-of-way signal is being displayed tophase A by local controller LC-l, as represented by closure of switch34. Once energized, relay CR3 remains energized by virtue of a holdingcircuit, defined by relay contacts C(R3-1 shunting cam circuit No. 3, solong as the phase A right-of-way signal is being displayed, i.e., solong as switch 34 remains closed.

The phase A setup interval No. 1 terminates when key P-1 actuatesmovable contact 64 to engage stationary contact 66, completing a circuitfor energizing step switch driver coil 72. This advances the step switch74 to interval No. 2 which may be termed as the phase A preventinterval. This timed interval is determined by the spacing between keyP-1 and key P2, and is preferably selected so as to correspond with thenormal initial right of-way interval that would be allocated bycontroller LC-l to phase A right-of-way movement so as to elimi nate thepossibility of allocating a right-of-way interval shorter than thenormal initial right-of-way interval. During phase A interval No. 2, camcircuit No. 3 is open. Accordingly, in the event that right-of-wayallocation to phase A started during prevent interval No. 2, relay CR3would not be energized. Likewise, if during this interval right-of-wayallocation to phase A is terminated, as represented by an open conditionof switch34, relay CR3, if previously energized duringthe phase A setupinterval No. 1, would now become de-energized. Interval No. 2 serves thepurpose of providing a period for preventing an output signal from beingcommunicated from the phase output circuit of coordination unit C1 tolocal controller LC-l in the event that a right-of-way interval was notbeing allocated by the controller to phase A prior to the termination ofphase A setup interval No. 1.

The phase A prevent interval is terminated when key P-2 actuates movablecontact 64 to engage stationary contact 66, completing a circuit forenergizing step switch driver coil 72. This advances the step switch tointerval No. 3 which may be termed as the phase A variable maximum timeout interval. During this period, cam circuit No. 4 is completed. Thetime duration of this interval is determined by the spacing between.keys P-2 and P-3. As previously, discussed, if right-of-way is allocatedto phase A during thephase A setup interval No. 1, relay CR3 isenergized through relay contacts CR3-1 during interval No. 3. Ifright-of-way is still being allocated to phase A during interval No. 3,switch 34 is closed and a circuit is completed through switch 34 inlocal controller LC-1, through the now completed cam circuit No. 4, andthe now closed relay contacts CR3-2 to the normally open relay contactsCR4-1. Upon energization of relay CR4 its contacts CR4-1 close tocomplete a circuit through the phase A output circuit of coordinationunit C-l to the phase A disabling switch 42 in local controller LC1 toenergize relay CR1. This energizes step switch driver coil 40, advancingphase A step switch 44. This actuates phase A signal circuit -46 toterminate allocation of a right-of-way interval to phase A and commencetiming a phase A clearance interval, after which phase A is deniedright-of-way movement. Relay CR4 is energized in response to a vehicleactuation of phase B vehicle actuatable detectors D-1, D-3 whichcompletes a circuit through the phase B memory circuit 32 to relay coilCR4-C. If phase B detectors D-l, D-3 are actuated prior to thetermination of phase A prevent interval No. 2, the actuation by key P-2of movable contact 64 to engage stationary contact 66 results intermination of the right-of-way allocation to phase A as soon as stepswitch 74 is advanced to the phase A variable maximum time out intervalNo. 3. In accordance with the invention, however, actuation of phase Bdetectors D-l, D-3 occurring any time during the phase A variablemaximum time out interval No. 3, also serves to terminate allocation ofright-of-way interval to phase A, since during interval No. 3 camcircuit No. 4 and relay contacts CR32 are closed requiring only theclosure of relay contacts CR41 to complete the phase A output circuit ofcoordination unit 0-1. The phase B vehicle actuation must, however,occur at a point in time in the background cycle prior to thetermination of interval No. 3, as determined by the location of key P-3,in order to terminate right-of-way allocation to phase A.

The phas'e A variable maximum time out interval No. 3 is terminated whenkey P-3 actuates movable contact 70 to engage stationary contact 66,completing a circuit for energizing step switch driver coil 72. Thisadvances the Step switch to interval No. 4 which may be termed as aphase A clearance interval. The timing of this interval is determined bythe spacing of keys P-3 and P-4, which preferably should be sufficientto provide a normal phase A clearance time interval in the event that aphase B vehicle actuation occurred just prior to the termination of thephase A variable maximum time out interval No. 3. This interval shouldalso be sufiiciently long in time duration to permit traffic controllerLC-l to change the signal displays so that right-of-way is allocated tophase B prior to the termination of the interval.

The phaseA clearance interval No. 4 is terminated when key P-4 actuatesmovable contact 64 to engage stationary contact 66, completing a circuitfor energizing step switch driver coil 72. This advances the step switch74 to the phase B setup interval No. 5. Interval No. 5 is similar to thephase A setup interval No. 1, discussed previously, and the timeduration of the interval is determined by the spacing between keys P-4and P5, which is preferably set to correspond with the normal initialright-of-way interval that would be allocated by local controller LC1 tophase B right-of-way movement. During the phase B setup interval No. 5,cam circuit No. 5 is completed to energize relay CR5 if a right-of-wayinterval is being allocated to phase B, as represented by closure ofswitch 36. Relay contacts CR5-1 and CR52 are closed, and contacts CR5-1parallel cam circuit No. 5 to complete a holding circuit for relay CR5.

.The. phase B setup interval is terminated when key P-5 actuates movablecontact 64 to engage stationary contact 66, completing a circuit forenergizing step switch driver coil 72. This advances the step switch tointerval No. 6 which may be termed as the phase B prevent interval.Interval No. 6 is similar to and serves the same purpose as the phase Aprevent interval No. 2 discussed previously.

If phase B right-of-way has been allocated prior to interval No. 6 toenergize relay CR5, then relay CR remains energized through its holdingcircuit, as defined by relay contacts CR5-1, during the phase B preventinterval.

The phase B prevent interval is terminated when key P-6 actuates movablecontact 64 to engage stationary contact 66, completing a circuit forenergizing step switch driver coil 72. This advances step switch 74 tointerval No. 7 which may be termed as the phase B variable maximum timeout interval. The time duration of this interval is determined by thespacing of keys P-6, P-7 and serves the same purpose as phase A variablemaximum time out interval No. 3 discussed previously. During thisinterval, cam circuit No. 6 is completed. Upon actuation of phase Aactuatable detectors D-2, D-4, a circuit is completed from the phase Amemory circuit 30 to energize relay CR6. This causes relay contactsCR6-1 to close. Accordingly, in a manner similar to that as discussedwith respect to the phase A coordination circuit J, a circuit iscompleted during the phase B variable maximum time out interval No. 7 tothe phase B output circuit of coordination unit C1, which leads to thephase B disabling switch 50. This causes energization of relay CR2 inlocal controller LC-l, advancing phase B step switch 54. This actuatesphase B signal circuit 56 to terminate allocation of a right-of-wayinterval to phase B and commence timing a phase B clearance interval,after which phase B is denied right-of-way movement.

The phase B variable maximum time out interval No. 7 is terminated whenkey P-7 actuates movable contact 64 to engage stationary contact 66,completing a circuit I for energizing the step switch driver coil 72.This advances the step switch 74 to interval No. 8 which may be termedas the phase A clearance interval. The time duration of this interval isdetermined by the spacing of keys P-7 and G and, in a manner similar tothe phase A clearance interval No. 4, the spacing is preferablysuflicient to provide a clearance interval for phase B in the event thatphase B right-of-way allocation was terminated at a point in time justprior to termination of interval No. 7. During this interval, camcircuit No. 2 is broken, i.e., open, in preparation for another cycle ofoperation.

The phase B clearance interval No. 8 is terminated when key G actuatesmovable contact 68 to engage stationary contact 70, completing a circuitfor energizing step switch driver coil 72. Cam circuit No. 1 iscompleted between interval Nos. 8 and 1 to render the dial motor selectcontrol circuitry effective to change the dial operation fromcoordination dial CD-l to coordination dial CD2 or (JD-3, dependent on aclosure of coordination dial selector switch DS-Z or DS3 located inmaster controller MC.

Whereas the background cycle timer has been described as taking the formof a synchronous motor driven coordination dial, the inventioncontemplates that other forms of timers may be used which have thecapability of actuating circuitry during selected points, i.e., at keysG and P-1 through P-7 of coordination dial CD-1, of the backgroundcycle. Similarly, whereas the background cycle divider circuit I hasbeen described in conjunction with dial keys, movable contacts and astep switch, the invention contemplates that this circuitry may bereplaced with suitable static, solid state, switching circuitry. Also,whereas the coordination circuits 1 and K have been described inconjunction with relay circuits, the invention contemplates that thiscircuitry may be replaced with static, solid state circuitry.

Although the invention has been shown and described in connection with apreferred embodiment, it will be readily apparent to those skilled inthe art that various changes in form and arrangement of parts may bemade to suit requirements.

Having thus described our invention, we claim:

1. A coordination unit for coordinating the operation of a full actuatedtraflic controller in an interconnected signalized system in response tothe receipt of signals from a master controller, said controller servingto control a traffic signal which displays go, caution and stopintervals to at least two traffic phases each having associatedtherewith traflic detector means for detecting traffic in said phase andregistering traffic demand with said controller, said controllerincluding go signal display means associated with each said phase for,upon energization, displaying a go interval display to said associatedphase, and switching circuit means associated with each said phase for,when energized, de-energizing said associated go signal display means tothereby terminate a go interval display to said associated phase; andcoordination unit adapted to be coupled to a said master controllercomprising: i

means for cyclically timing a background cycle having a predeterminedtime duration; means for dividing said background cycle into at leasttwo successively timed intervals associated with each of said phases;and,

said coordination unit includes for each said phase:

phase termination means for, when energized, en-

ergizing the associated said switching circuit means in said controller;

means responsive during the first of said associated intervals to a gosignal to said associated phase for conditioning said phase terminationmeans for subsequent energization; and,

means responsive substantially upon the termination of said secondinterval to a trafiic detection by a said detector means associated withanother said phase for energizing said switching circuit means tothereby terminate a go interval display to said associated phase.

2. A coordination unit as set forth in claim 1 wherein said dividingmeans divides said background cycle so as to include for each phase athird potential interval of a maximum timed duration and which commencessubstantially upon termination of said second interval.

3. A coordination unit as set forth in claim 2 wherein said traflicdetection responsive means is responsive only during said potentialinterval to a said traffic detection for energizing said phasetermination means.

4. A coordination unit as set forth in claim 1 wherein said backgroundcycle timing means includes a motor driven coordination dial and whereinsaid dividing means is adjustable for adjustably dividing saidbackground cycle into timed intervals of desired timed durations andincludes a plurality of switch actuator keys carried by fiat? dial atpreselected angularly spaced locations on said 5. A coordination unit asset forth in claim 1 wherein each said go signal display responsivemeans includes a first relay coil, and each said phase termination meansincludes first normally open relay contacts associated with said firstrelay coil and closed upon energization of said first relay coil.

=6. A coordination unit as set forth in claim 5 wherein said trafficdetection responsive means includes a second relay coil, and each saidphase termination means includes second normally open relay contactsconnected with said first relay contacts and closed to complete acircuit with said first relay contacts upon energization of said secondcoil, and output circuit means connected with said relay contacts andadapted to be connected to said associated go interval termination meansin said controller.

7. A plurality of coordination units each for coordinating the operationof a like plurality of full actuated local traffic controllers inresponse to the receipt of signals from a master controller, said mastercontroller including circuit means for developing a pattern of saidsignals according to a predetermined program, each said trafliccontroller serves to allocate go and stop tratfic signal intervals to atleast first and second traffic actuatable phases displaying a gointerval display to said associated phase,

and sequencer switching means associated with each said phase for, whenenergized, de-energizing said associated go signal display means tothereby terminate a said go interval display to said associated phase;each said coordination unit being associated with and coupled to one ofsaid plurality of traffic controllers and adapted to receive signalsfrom a'said master controller and comprising:

means forvcyclically timing a background cycle having -a predeterminedtime duration;

means for dividing said background cycle'into a plurality ofsuccessivelytimed intervals associated with each of saidphases;

first, second, -third and fourth switching means associated with eachsaid phase, each said switching means having a normal'first conditionand asecond condisaid first and second switching means being controlledby said dividing means in such a manner" that they are respectively intheir second conditions only during a first and a second of said timedintervals asso ciated with said phase, each said first and secondswitching means connected with a coordination unit input circuit adaptedto be connected with an energizing source when said associated localcontroller is allocating a go interval to said associated phase;

bistable means associated with each phase and having a normal firststate and a second state, said bistable means being controlled by saidfirst switching means so as to be actuated to its second state only whensaid first switching means is in its second condition and is connectedto a said energizing source;

said third switching means being controlled by said associated bistablemeans so as to be in its second condition only when said bistable meansis in its second state;

means for actuating said fourth switching means to its second condition,said actuating means adapted to be connected to an energizing source foractuating said fourth switching means to its second condition only inresponse to an actuation of another said phase to which a stop intervalis being allocated by said associated local controller; and,

a coordination output circuit associated with each said phase andadapted to be connected to a go interval termination means in saidassociated local controller for terminating allocation of a said gointerval to said associated phase; 5 said second, third and fourthswitching means being interconnected in such a manner that said outputcircuit connects said go interval termination means with a saidenergizing source only when said second, third and fourth switchingmeans are in their second conditions whereupon said terminating means insaid associated local controller is energized to terminate allocation ofsaid go interval to said associated phase. 8. A coordination unit as setforth in claim 7 wherein said bistable means includes a relay coil andsaid third switching means includes normally open relay contactsactuated to a closed condition upon energization of said relay coil. I

9. A coordination unit as set forth in claim 7 wherein said bistablemeans includes a relay coil and a holding circuit connecting said coilto said source of energy for maintaining said bistable means in itsecond condition when said first switching means returns to its firstcondition. I h p 10. A coordination unit as set forth in claim 9 whereinsaid holding circuit includes normally open relay contac't actuated to aclosed condition upon energization of said relay coil.

11. A coordination unit as set forth in claim 7 wherein said actuatingmeans includes a relay coil and said fourth switching means includesnormally open relay contacts actuated to a closed condition uponenergization of said relay coil. w

12; A coordination unit as set forth in claim 7 wherein said second,third and fourth switching means define'an AND circuit requiring saidswitching means to be in their second condition for completing anenergizing circuit to said associated coordination-output circuit.-

13; A coordination unit as set forth in claim 7' wherein said backgroundcycle timing means includes a synchronous motor'drivencoordination dial;and said dividing meansincludes:

a plurality ofmov-able contact actuator keys extending-radially. outwardfrom said dial and arcuately spaced from each othen in a predeterminedpattern; and," v r a movablecontact means actuatable by said keys forcompleting,"upon actuation, an energizing circuit for a said sequencerswitching means.

'14. A'method of coordinating the operation of a full act'uated-trafiiccontroller which controls allocations .of

go, caution and stop intervals to at least tWo-trafiic phases,

each having. traflic' detector means associated therewith for detectingtraffic and registering tr-afiic demands with said controller; .0 t

said method comprising the steps of? timing a background cycle having apredetermined time duration; v

dividing said background cycle into at least two successively timedintervals associated with each said phase controlled bysaid controller;

during the first of said intervals,

sensing whether said controller is allocating a go Signal interval tosaid associated phase;

conditioning phase termination circuit means, only when a said go signalinterval allocation is sensed, to a condition whereupon whensubsequently energized it will terminate said go signal interval;

sensing for the occurrence of a trafiic detection by a said detectormeans associated with another said phase; and,-

energizing said phase termination circuit means, only after terminationofisaid second interval and when a said traffic actuation is sensed, toterminate said go signal interval to saidassociated phase. 15. A methodas set forth in claim 14 including the further. step of:. I

dividing said background cycle so as to include a third timedintervalhaving a maximumtime duration so a that said third interval, commencessubstantially, im-

mediately upon termination of said second interval.

'16. A method as set forth in claim 15 including the further step of; rv

continuing said trafiic detection sensing step during said thirdinterval until a said traflic actuation detection is sensed or. saidthird interval is terminated upon said maximum time duration, which everoccurs first.

17. A method as set forthvin claim 16 including the further steptofz V 7v dividingsaid background cycle so asto include a timed clearanceinterval which commences substantially immediately upon termination ofsaid third interval.

18; A method as set forth in claim 17 including the further step of: n V

commencing, substantially immediately upon the termination of saidclearance interval, the first of said timed intervals associated withanother ofsaid phases. I

19. A coordination'unit' as set forth in claim 7 wherein said secondswitching means, said third switching means, said fourthjswitching meansand said go interval terminating means are each coupled in seriesconnection with each other;

said first switching means, said bistable means, said means foractuating said fourth switching means said means for actuating saidfourth switching means, and terminating means in said local controlleris enersaid detector means associated with another said gized toterminate actuation of said go interval to phase are each coupled inseries connection with said associated phase. each other; 5

said bistable means and said means for actuating said R e ces CltedfOllIth switching means being coupled directly 110 UNITED STATES PATENTSeach other so as to define a junction point; and,

said junction point being coupled to a said energizing $52 gig 3g SourceWhereln When said first switching means is 10 3,208,038 9/1965 Jeffers340 35 actuated to its second condition said bistable means is energizedto thereby actuate said third switching THOMAS HABECKER, p i Examinermeans to its second condition and when said second switching means isactuated to its second condition a US. Cl. X.R.

circuit is completed so that upon energization of said 15 340-37

